There are a number of instances in mammalian systems where nutritional factors apparently regulate the level of specific enzymes. For example, a number of enzymes involved in the biosynthesis of fat increase in concentration when rats are fed high carbohydrate-fat free diets. Two of these enzymes, glucose-6-PO4 dehydrogenase and 6-PO4 gluconate dehydrogenase are regulated such that the rate of synthesis is proportional to the dietary consumption of carbohydrate. In addition cyclic AMP decreases the rate of synthesis of glucose-6-PO4 dehydrogenase. These two enzymes will be used as model systems to study the mechanisms by which hormones and diet regulate the synthesis of lipogenic enzymes. The concentration of mRNA coding for the synthesis of each enzyme will be measured by the use of I125 antiserum or by the translation of the mRNA. If diet or cyclic AMP act at the translational level an in vitro system will be used to determine the mechanism by which these factors regulate the translation of lipogenic enzymes.